Replication between servers that are intermittantly connected

I have an interesting scenario I'm working on and I'd like some feedback if
anyone's ever had to cope with something similar.
Three oracle servers replicating data to a master fourth system, with a
subset of the master data being replicated back.
The servers are not always connected to the network. The network connection
comes and goes in a semi random manner, although once the connection has
been up for more than around 20 minutes, it's likely to stay up for two or
three hours before going down again.

My original thoughts were to ship data back and forwards using IBM's Message
Queue (which we already use throughout the company) and write a load/merge
process to load the data - but after reading up a bit about Oracle Streams,
I'm starting to think that I might be able to do it all within an Oracle
environment. Does anyone have experience using streams in an unstable
environment like this ?

The servers themselves and the DBs on them stay up all the time - it's the
actual network link I'll loose.